>/sys/kernel/debug/kmemleak output: backtrace not printed since 6.2.0-rc1
>
>
>>On 12. 01. 2023. 20:50, Mirsad Todorovac wrote:
>>> Hi all,
>>>
>>> there seems to be a problem with the output of
>>/sys/kernel/debug/kmemleak:
>>>
>>> [root@pc-mtodorov ~]# cat /sys/kernel/debug/kmemleak unreferenced
>>> object 0xffff951c118568b0 (size 16):
>>> comm "kworker/u12:2", pid 56, jiffies 4294893952 (age 4356.548s)
>>> hex dump (first 16 bytes):
>>> 6d 65 6d 73 74 69 63 6b 30 00 00 00 00 00 00 00 memstick0.......
>>> backtrace:
>>> [root@pc-mtodorov ~]#
>>>
>>> Apparently, backtrace of called functions on the stack is no longer
>>> printed
>>with the list of memory leaks.
>>>
>>> This appeared on Lenovo desktop 10TX000VCR, with AlmaLinux 8.7 and
>>> BIOS version M22KT49A (11/10/2022) and 6.2-rc1 and 6.2-rc2 builds.
>>>
>>> This worked on 6.1 with the same CONFIG_KMEMLEAK=y and MGLRU
>>enabled
>>> on a vanilla mainstream kernel from Mr. Torvalds' tree. I don't know
>>> if this is
>>deliberate feature for some reason or a bug.
>>>
>>> Please find attached the config, lshw and kmemleak output.
>>>
>>> The bisection gave this commit as the culprit for the severed stack
>>> backtrace print in /sys/kernel/debug/kmemleak:
>>>
>>> mtodorov@domac:~/linux/kernel/linux_torvalds$ git bisect good
>>> 56a61617dd2276cbc56a6c868599716386d70041 is the first bad commit
>>> commit 56a61617dd2276cbc56a6c868599716386d70041
>>> Author: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>>> Date: Thu Oct 27 17:50:24 2022 +0800
>>>
>>> mm: use stack_depot for recording kmemleak's backtrace
>>>
>>> Using stack_depot to record kmemleak's backtrace which has been
>>> implemented on slub for reducing redundant information.
>>>
>>> The complete bisect log is:
>>>
>>> mtodorov@domac:~/linux/kernel/linux_torvalds$ git bisect log git
>>> bisect start '--' 'mm'
>>> # good: [830b3c68c1fb1e9176028d02ef86f3cf76aa2476] Linux 6.1 git
>>> bisect good 830b3c68c1fb1e9176028d02ef86f3cf76aa2476
>>> # bad: [1b929c02afd37871d5afb9d498426f83432e71c2] Linux 6.2-rc1 git
>>> bisect bad 1b929c02afd37871d5afb9d498426f83432e71c2
>>> # good: [8b9ed79c2d587bec5f603d66801478a5af9af842] Merge tag
>>> 'x86_asm_for_v6.2' of
>>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>>> git bisect good 8b9ed79c2d587bec5f603d66801478a5af9af842
>>> # good: [e83b39d6bbdb6d25bd6f5c258832774635d29b47] mm: make
>>> drop_caches keep reclaiming on all nodes git bisect good
>>> e83b39d6bbdb6d25bd6f5c258832774635d29b47
>>> # good: [9997bc017549acd6425e32300eff28424ffeeb6b] zsmalloc:
>>implement
>>> writeback mechanism for zsmalloc git bisect good
>>> 9997bc017549acd6425e32300eff28424ffeeb6b
>>> # good: [6287b7dae80944bfa37784a8f9d6861a4facaa6e] mm,thp,rmap: fix
>>> races between updates of subpages_mapcount git bisect good
>>> 6287b7dae80944bfa37784a8f9d6861a4facaa6e
>>> # good: [8fa590bf344816c925810331eea8387627bbeb40] Merge tag
>>> 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
>>> git bisect good 8fa590bf344816c925810331eea8387627bbeb40
>>> # good: [4f292c4de4f6fb83776c0ff22674121eb6ddfa2f] Merge tag
>>> 'x86_mm_for_6.2_v2' of
>>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>>> git bisect good 4f292c4de4f6fb83776c0ff22674121eb6ddfa2f
>>> # bad: [1ea9d333ba475041efe43d9d9bc32e64aea2ea2b] Merge tag
>>> 'mm-stable-2022-12-17-2' of
>>> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
>>> git bisect bad 1ea9d333ba475041efe43d9d9bc32e64aea2ea2b
>>> # bad: [56a61617dd2276cbc56a6c868599716386d70041] mm: use
>>stack_depot
>>> for recording kmemleak's backtrace git bisect bad
>>> 56a61617dd2276cbc56a6c868599716386d70041
>>> # good: [61b963b52f59524e27692bc1c14bfb2459e32eb3] mm/gup_test:
>>free
>>> memory allocated via kvcalloc() using kvfree() git bisect good
>>> 61b963b52f59524e27692bc1c14bfb2459e32eb3
>>> # first bad commit: [56a61617dd2276cbc56a6c868599716386d70041] mm:
>>use
>>> stack_depot for recording kmemleak's backtrace # good:
>>> [9102b78b6f6ae6af3557114c265c266b312c1319] maple_tree: update
>>> copyright dates for test code git bisect good
>>> 9102b78b6f6ae6af3557114c265c266b312c1319
>>> # first bad commit: [56a61617dd2276cbc56a6c868599716386d70041] mm:
>>use
>>> stack_depot for recording kmemleak's backtrace You have mail in
>>> /var/mail/mtodorov mtodorov@domac:~/linux/kernel/linux_torvalds$
>>>
>>> The platform is 10TX000VCR
>>(LENOVO_MT_10TX_BU_Lenovo_FM_V530S-07ICB)
>>> running AlmaLinux 8.7 (CentOS clone) and BIOS M22KT49A.
>>>
>>> GCC used was:
>>>
>>> mtodorov@domac:~/linux/kernel/linux_torvalds$ gcc --version gcc
>>> (Debian 8.3.0-6) 8.3.0 Copyright (C) 2018 Free Software Foundation,
>>> Inc.
>>> This is free software; see the source for copying conditions. There
>>> is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
>>PARTICULAR PURPOSE.
>>> mtodorov@domac:~/linux/kernel/linux_torvalds$
>>>
>>> Hope this helps.
>>>
>>> I lack the insight to pinpoint the exact fault in the patch.
>>
>>P.S.
>>
>>To further complicate things, on Ubuntu 22.10 Lenovo Ideapad 3 15ITL6
>>laptop the kmemleak stack backtrace is printed correctly with the same
>>kernels (but .deb instead of .rpm for the same build):
>>
>>unreferenced object 0xffff94ca88e042d0 (size 80):
>> comm "thermald", pid 768, jiffies 4294893592 (age 78581.504s)
>> hex dump (first 32 bytes):
>> 00 00 00 00 00 00 00 00 0d 01 2d 00 00 00 00 00 ..........-.....
>> af 07 01 80 fd ac ff ff 00 00 00 00 00 00 00 00 ................
>> backtrace:
>> [<ffffffffa0dcb921>] slab_post_alloc_hook+0x91/0x320
>> [<ffffffffa0dcfb79>] kmem_cache_alloc+0x169/0x2f0
>> [<ffffffffa12b1def>] acpi_os_acquire_object+0x2c/0x32
>> [<ffffffffa12b1ea2>] acpi_ps_alloc_op+0x4a/0x99
>> [<ffffffffa12af5c8>] acpi_ps_get_next_arg+0x611/0x761
>> [<ffffffffa12afbbc>] acpi_ps_parse_loop+0x494/0x8d7
>> [<ffffffffa12b1434>] acpi_ps_parse_aml+0x1bb/0x561
>> [<ffffffffa12b24c8>] acpi_ps_execute_method+0x20f/0x2d5
>> [<ffffffffa12a7acf>] acpi_ns_evaluate+0x34d/0x4f3
>> [<ffffffffa12ad6a3>] acpi_evaluate_object+0x180/0x3ae
>> [<ffffffffa1269ca8>] acpi_run_osc+0x128/0x250
>> [<ffffffffc0bbb14f>] int3400_thermal_run_osc+0x6f/0xc0
>>[int3400_thermal]
>> [<ffffffffc0bbb293>] current_uuid_store+0xe3/0x120 [int3400_thermal]
>> [<ffffffffa13b8ed4>] dev_attr_store+0x14/0x30
>> [<ffffffffa0ee0458>] sysfs_kf_write+0x38/0x50
>> [<ffffffffa0edf516>] kernfs_fop_write_iter+0x146/0x1d0 You have new
>>mail in /var/mail/root root@marvin-IdeaPad-3-15ITL6:/home/marvin#
>>
>>Regards,
>>Mirsad
>
>thanks for head up. Could you please help to check If CONFIG_STACKTRACE
>and CONFIG_STACKDEPOT is enabled on the fault kernel?
Please try the patch below if the configs are right. I think it should be caused by the late ready for kmemleak
commit 556eb1927da99ab366e370d593fc32da946768c3
Author: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
Date: Fri Jan 13 14:13:39 2023 +0800
mm: instroduce a flag to indicate stack_depot's ready
try to solve the kmemleak's late ready issue.
diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 762b91f..7eb24bc 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -216,6 +216,7 @@ struct kmemleak_object { static int kmemleak_warning;
/* set if a fatal kmemleak error has occurred */ static int kmemleak_error;
+static int kmemleak_stadep_initialized;
/* minimum and maximum address that may be valid pointers */ static unsigned long min_addr = ULONG_MAX; @@ -601,7 +602,7 @@ static noinline depot_stack_handle_t set_track_prepare(void)
unsigned long entries[MAX_TRACE];
unsigned int nr_entries;
- if (!kmemleak_initialized)
+ if (!kmemleak_stadep_initialized)
return 0;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT); @@ -2110,6 +2111,7 @@ void __init kmemleak_init(void)
create_object((unsigned long)__start_ro_after_init,
__end_ro_after_init - __start_ro_after_init,
KMEMLEAK_GREY, GFP_ATOMIC);
+ kmemleak_stadep_initialized = 1;
}
>>
>>--
>>Mirsad Goran Todorovac
>>Sistem inženjer
>>Grafički fakultet | Akademija likovnih umjetnosti Sveučilište u Zagrebu
>>
>>System engineer
>>Faculty of Graphic Arts | Academy of Fine Arts University of Zagreb,
>>Republic of Croatia The European Union
